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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
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    <title>金字塔</title>
    <script>
        var level=prompt ('请设置金字塔的层数');
        level = parseFloat(level)&&Number(level);
        if (isNaN(level)){
            alert('金字塔的层数必须是数字');
        }
        for (var i=1;i<=level;i++){
            var blank=level - i;
            for(var k=0;k<blank;k++){
                document.write('&nbsp;');
            }
            var star=i*2-1;
            for(var j=0;j<star;++j){
                document.write('*');
            }
            document.write('<br>');

        }
        
    
    </script>
<p><a href="第二章.html">返回上一级</a></p>
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</body>
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